SEOUL -- In a ceremony attended by South Korean President Moon Jae-in and Crown Prince Mohammed bin Salman of Saudi Arabia, S-Oil controlled by Saudi Aramco officially opened new petrochemical facilities at its production base in the southeastern industrial city of Ulsan.

This is S-Oil's first massive investment project since Saudi Aramco, the world’s largest oil exporter, became its largest shareholder in 2014. It was the largest petrochemical plant construction project in South Korea.

The project includes facilities for a residue-upgrading complex, which converts residues left after extracting gas and light oil from crude oil into high-valued products, and an olefin downstream complex which produces propylene oxide and polypropylene.

Saudi Aramco, Saudi Arabia's state-run oil giant, bought a 35 percent stake in S-oil in 1991 and increased its stake to 65 percent in 2014. The ceremony on Wednesday took place in Seoul.